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https://github.com/systemd/systemd
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82c2214539
A fixed name is too rigid, let's give users the ability to define custom drop-in names which at the same time also allows defining multiple dropins per unit. We use ~ as the separator because: - ':' is not allowed in credential names - '=' is used to separate credential from value in mkosi's --credential argument. - '-' is commonly used in filenames - '@' already has meaning as the unit template specifier which might be confusing when adding dropins for template units
115 lines
5.6 KiB
XML
115 lines
5.6 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-debug-generator" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-debug-generator</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-debug-generator</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-debug-generator</refname>
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<refpurpose>Generator for enabling a runtime debug shell and
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masking specific units at boot</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/usr/lib/systemd/system-generators/systemd-debug-generator</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-debug-generator</filename> is a generator
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that reads the kernel command line and understands three
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options:</para>
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<para>If the <option>systemd.mask=</option> or <option>rd.systemd.mask=</option>
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option is specified and followed by a unit name, this unit is
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masked for the runtime (i.e. for this session — from boot to shutdown), similarly to the effect of
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>mask</command> command. This is useful to boot with
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certain units removed from the initial boot transaction for
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debugging system startup. May be specified more than once.
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<option>rd.systemd.mask=</option> is honored only by initial
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RAM disk (initrd) while <option>systemd.mask=</option> is
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honored only in the main system.</para>
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<para>If the <option>systemd.wants=</option> or
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<option>rd.systemd.wants=</option> option is specified
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and followed by a unit name, a start job for this unit is added to
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the initial transaction. This is useful to start one or more
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additional units at boot. May be specified more than once.
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<option>rd.systemd.wants=</option> is honored only by initial
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RAM disk (initrd) while <option>systemd.wants=</option> is
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honored only in the main system.</para>
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<para>If the <option>systemd.debug_shell</option> or <option>rd.systemd.debug_shell</option> option is
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specified, the debug shell service <literal>debug-shell.service</literal> is pulled into the boot
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transaction and a debug shell will be spawned during early boot. By default,
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<filename>&DEBUGTTY;</filename> is used, but a specific tty can also be specified, either with or without
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the <filename>/dev/</filename> prefix. To set the tty to use without enabling the debug shell, the
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<option>systemd.default_debug_tty=</option> option can be used which also takes a tty with or without the
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<filename>/dev/</filename> prefix. Note that the shell may also be turned on persistently by enabling it
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with <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>enable</command> command. <option>rd.systemd.debug_shell</option> is honored only by initial
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RAM disk (initrd) while <option>systemd.debug_shell</option> is honored only in the main system.</para>
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<para><filename>systemd-debug-generator</filename> implements
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>System Credentials</title>
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<variablelist class='system-credentials'>
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<varlistentry>
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<term><varname>systemd.extra-unit.*</varname></term>
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<listitem><para>Credentials prefixed with <literal>systemd.extra-unit.</literal> specify additional
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units to add to the final system. Note that these additional units are added to both the initrd and
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the final system. <varname>ConditionPathExists=!/etc/initrd-release</varname> can be used to make
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sure the unit is conditioned out in the initrd. Note that this can also be used to mask units, by
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simply specifying an empty value.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.unit-dropin.*</varname></term>
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<listitem><para>Credentials prefixed with <literal>systemd.unit-dropin.</literal> add drop-ins for
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the corresponding units in the final system. Each credential must be suffixed with the full unit name
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including the unit extension. Its contents must be a valid unit drop-in file. Optionally, the unit
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name may be followed with <literal>~</literal>, followed by the drop-in name without the
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<literal>.conf</literal> suffix. If not specified, the name of the generated drop-in will be
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<literal>50-credential.conf</literal>. Note that these additional drop-ins are added to both the
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initrd and the final system.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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